Direct reduction of metallic oxides in dynamic hydrogen atmosphere

ABSTRACT

PROCESS FOR REDUCING OXIDES OF METALLIC ELEMENTS FROM GROUP III AND IV OF THE PERIODIC TABLE BY REACTION WITH MAGNESIUM IN A DYNAMIC HYDROGEN ATMOSPHERE. MAGNESIUM OXIDE FORMED DURING THE REACTION IS CARRIED AWAY   FROM THE REACTION ZONE IN THE HYDROGEN GAS FLOW AND DEPOSITED AT A REMOTE LOCATION.

Aug.3, 1971 J, KANTER 3,597,157

DIRECT REDUCTION Ob METALLIC OXIDES IN DYNAMIC HYDROGEN ATMOSPHERE Filed April 1'7, 1968 y; if

L/ZM/W f A United States Patent O 3,597,157 DIRECT REDUCTION OF METALLIC OXIDES IN DYNAMIC HYDROGEN ATMOSPHERE Jerome J. Kanter, Palos Park, Ill., assignor to Crane Co., Chicago, Ill. Filed Apr. 17, 1968, Ser. No. 722,033 Int. Cl. C01b 6/06; C01f /04 U.S. Cl. 23--204R 8 Claims ABSTRACT OF THE DISCLOSURE Process for reducing oxides of metallic elements from Group III and IV of the Periodic Table by reaction with magnesium in a dynamic hydrogen atmosphere. Magnesium oxide formed during the reaction is carried away from the reaction zone in the hydrogen gas fiow and deposited at a remote location.

BACKGROUND OF THE INVENTION This invention relates in general to the reduction of metal oxides. It deals more particularly with the reduction of the oxides of metallic elements from Groups III and IV of the Periodic Table.

The process normally utilized to reduce metallic oxides, specifically those involving Groups III and 1V elements, is both complicated and expensive. It conventionally consists of a carburization step followed by halogenation. The latter step is, in turn, followed by either a thermic reduction or electrolysis.

As is well-known, the aforedescribed process produces the element in its metallic form. In certain cases, however, the Groups III and IV metals are readily usable in reduced but combined form; as a hydride, for example. In addition, the hydride itself can usually be processed to elemental form without complicated or expensive treatment. Accordingly, the reduction of a metal oxide to its hydride has been considered and attempts made to develop a practical porcess for this type of reduction.

In the late 1880s, a German, C. A. Winkler, discovered that Group III and IV metal hydrides could be obtained from the metal oxides by subjecting the oxides to high temperatures in the presence of magnesium and a static hydrogen atmophere. Wrinkler was unable, however, to produce the hydride except in a mixture with magnesia, MgO. Consequently, Winkers work proceeded no further in this direction.

In the 1940s, L. W. Davis disclosed, in US. Pat. No. 2,411,524, a process for reducing zirconium oxide to its hydride by this process. However, Davis considered his process limited in application and it was. Henrie et al., in US. Pat. No. 3,140,170, used the basic process on titanium. They, however, found it necessary to employ an acid leaching step to remove magnesia and obtain a usable hydride.

SUMMARY OF THE INVENTION The present invention is embodied in an improved process for reducing Groups III and IV metal oxides to their hydrides. A primary object is to provide such a process which is simpler, less expensive and more effective than the broadly similar processes heretofore known.

The foregoing and other objects of the invention are realized in a process for reducing Groups III and IV metallic element oxides with a Groups I and II metal, in a dynamic hydrogen atmosphere. The Group I or II metal, which might be magnesium, sodium or calcium, forms a solid oxide, magnesia, while the Group III or IV element, lanthanum or titanium, for example, is reduced to its hydride. According to the invention, a continuous flow of hydrogen gas through the system completely removes the 3,597,157 Patented Aug. 3, 1971 'ice magnesia from the system, leaving a substantially pure hydride as its product. At the same time, the pure magnesia is deposited in a cake for ready access and profitable disposal.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing, a simple laboratory system for practicing the process of the invention is illustrated generally at 9. In this light, the system 9 is merely exemplary of systems which might be employed in laboratory practice of the invention process or larger commercial systems.

The system 9 includes a conventional electric mufile furnace 10. Inside the furnace 10 is a retort 11 which is preferably fabricated of cast iron or the like. The retort defines a reduction chamber 12 into which a charge prepared according to the invention is placed. An exemplary charge will hereinafter be discussed in a description of the practice of the invention process.

Extending into the furnace and communicating with one end of the retort 11 is a steel inlet pipe 15. The steel pipe 15 originates at a source of hydrogen, here illustrated as a hydrogen cylinder 16, having a flow control valve assembly 17 at its outlet.

Extending from the opposite end of the muffie furnace 10 and communicating with the retort 11 inside the furnace is a steel outlet pipe 20. The steel outlet pipe 20 is, in turn connected at a joint 21 to a generally U-shaped copper pipe 22. The copper pipe 22 extends downwardly into a chilling tank 25 containing a chilling solution in the form of cold water, for example, seen generally at 26. The base 28 of the U-shaped pipe 22 forms, for reasons hereinafter discussed, a trap deep within the confines of the coolant solution 26.

Joining the copper pipe 22 to the inlet pipe 15 is a return pipe 29. The return pipe 29 is connected to the copper pipe 22 at a joint 30 and to the pipe 15 at a T connection 31. Disposed in the pipe 29 intermediate its ends are a conventional gas fiow booster pump 35 and a filter 36 of any well-known type for filtering impurities from hydrogen gas.

The process of the invention is best described by way of example. In laboratory practice, a mixture of 60 mesh calcined rare earth oxide and magnesium granules, mixed four (4) parts of the oxide to one 1) part metallic magnesium, was introduced into the retort 11. The retort was place in the furnace 10 and placed in communication at its opposite ends with the hydrogen flow pipes 15 and 20. A constant flow of hydrogen through the retort 11 was then instituted by manipulation of the control valve 17, the hydrogen flowing from the pipe 15 through the retort 11 and out through the pipe 20.

The flow of hydrogen was adjusted to about four liters per minute and the furnace ignited. The temperature in the furnace rose to 1,500 P. Above about 800 F. a hydrogen flame burned within the furnace and this flame turned from colorless to white as it became saturated with a smoke composed of magnesium oxide particles.

The dynamic flow of hydrogen carried the magnesia smoke out of the retort 11 and through the copper pipe 22 into the trap 28 disposed in the coolant solution 26. Rapid cooling of the hydrogen entrained magnesium oxide particles caused the particles to be deposited in a cake on the inner wall of the trap 28 while the hydrogen continued its flow, drawn by the booster pump 35.

The hydrogen was passed on by the booster pump 35 through the impurity filter 36, which acts as a chemical trap to remove impurities from the hydrogen. This purified hydrogen passed through the T joint to the inlet pipe 15 and once more circulated through the system in the aforedescribed manner.

When smoke was no longer apparent in the flow of hydrogen out of the retort 11, the reaction was completed and the furnace cooled with continous hydrogen flow. After cooling, the product of the reaction process according to the invention was a black powder comprising the rare earth hydride.

The hydride which is the end product of the invention process is virtually free of magnesia. It can readily be used without a further purification process, unlike the product of the process disclosed in the aforementioned Henrie et al. patent, for example. Where desirable, this hydride product can be processed to its metal by introducing it into a suitable vacuum melting furnace. The hydrogen gas is disspelled and the metal melted to ingot form.

A further attractive feature of the process embodying the invention is the accumulation of pure magnesia in the trap. Pure magnesia has a commercial value which more than returns the cost of the magnesium, for example.

While the exemplary system described herein is at present considered to be preferred, it is understood that various modifications and improvements may be made therein, and it is intended to cover in the appended claims all such modifications and improvements as fall within the true spirit and scope of the invention.

What is desired to be claimed and secured by Letters Patent of the United States is:

1. A process for reducing the oxides of metals, the steps comprising:

heating in a reduction zone under a hydrogen gas atomsphere at least one metal oxide in the presence of magnesium to temperatures sufiicient to cause the reduction of said metal oxide to the corresponding hydried whereby there is produced magnesium oxide in finely divided form,

said metal oxide selected from oxides of metals consisting of Groups III and IV of the Periodic Table, producing a dynamic flow of the hydrogen gas during the reduction operation through a closed system containing the reduction zone in which the reaction of said metal oxide with said magnesium occurs in order that the magnesium oxide formed during said reaction will be entrained in the hydrogen gas, said hydrogen gas flow produced at rates during said reduction operation sufficient to carry away the finely divided magnesium oxide from said metal hydride,

conducting the flow of hydrogen gas with the entrained magnesium oxide through said system away from and to a point spaced from said reduction zone during said reduction operation, and

separating said magnesium oxide from the hydrogen gas at an area remote from said reduction zone in order to keep said magnesium oxide from contaminating the metal hydride.

2. The process of claim 1 further characterized by and including the step of continuing to pass hydrogen gas through said reduction zone after said hydride has been formed and said heating has been discontinued.

3. The process of claim 1 further characterized by separating the magnesium oxide from said hydrogen gas by passing the hydrogen flowing from said reduction zone through cooling means in order that the finely divided magnesium oxide is deposited on a surface in said cooling means.

4. The process of claim 1 further characterized by recirculating the hydrogen gas to said reduction zone after passing said separating step.

5. The process of claim 1 in which said metal oxide is a Group III metal oxide.

6. The process of claim 1 in which said metal oxide is a Group IV metal oxide.

7. The process of claim 1 in which said metal oxide is a rare earth oxide.

8. The process of claim 1 in which said metal oxide is titanium oxide.

References Cited UNITED STATES PATENTS 2,411,524 11/1946 Davis 23-204 OSCAR R. VERTIZ, Primary Examiner H. S. MILLER, Assistant Examiner US. Cl. X.R. 23186 

